You can access the Availability page on mobile by tapping the 'tick' icon at the top-right of the Shifts page.
This page shows a list of your existing patterns. You can edit a pattern by tapping on it, or delete it by swiping to the left. You can add a new pattern using the "+" button.
Creating/Editing an Availability Pattern
Enter a Title for the pattern, and set the Effective Dates (If you choose "Specific Dates", you'll need to enter a start date, end date, and how often you'd like the pattern to repeat.)
Below, you'll see a list containing the 7 days of the week. Each day has two buttons: Add Availability and Add Unavailability. Using those buttons, you can set periods during each day of the week when you're available/unavailable. You can add as many periods of availability and unavailability per day as you need.
When you're done setting all that up, hit the "Save" button in the top-right of the screen.